This invention relates generally to variable stroke, variable displacement, four cycle internal combustion engines. More specifically, the present invention deals with an improved articulated connecting rod linkage and a pressure-responsive control therefor operable to vary the stroke of the engine piston in response to variations of pressures within the fuel induction system of the engine and thereby provide for substantially uniform compression of any fuel charge inducted into the cylinder of the engine prior to firing.
The most pertinent known prior art is typified by U.S. Patent Nos. 2,822,791; 2,873,611; 2,909,163 and 2,909,164 issued to one Arnold E. Biermann. These prior art patents, as well as others, disclose generally the concept of varying the stroke and displacement of an internal combustion engine by utilizing an adjustable articulated connecting rod linkage between the engine piston and the crankshaft. However, the known prior art variable stroke engines are generally characterized by relatively complex, multiple linkage systems which would increase power loss due to added friction and inertia of the multitude of moving parts. Further, so far as the applicant is aware, no one has heretofore proposed an internal combustion engine having an articulated connecting rod linkage which is operable automatically to vary the stroke of the engine piston in accordance with fuel induction pressures so that a low density fuel charge may be compressed to substantially the same pressure at the time of firing as a relatively higher density fuel charge, thereby adding greatly to the efficiency of the engine, particularly during low throttle operations.
As will be well understood by those familiar with internal combustion engine design, present day fixed stroke engines are designed to provide maximum operating efficiency at full or open throttle. That is, the stroke and compression ratio of an internal combustion engine is generally calculated to provide for optimum compression of the denser fuel charges inducted into the engine's cylinder under open throttle conditions. Thus, when the engine throttle is moved to a closed or idle position, the density of the fuel charge inducted into the combustion cylinder is considerably reduced, with the result that the less dense fuel charge will not be compressed to the same, optimum pressure as would a denser open-throttle charge. Failure to compress a fuel-air mixture to a given high pressure at the time of firing results in inefficient burning of the fuel with consequent wastage and exhaust pollution problems.
Another objectionable feature of present day internal combustion engines is the excess wear and loss of power caused by lateral or radially directed forces applied to the piston through the connecting rod as it oscillates laterally back and forth through the axis of the cylinder. Any time the connecting rod occupies an angular position with respect to the axis of the cylinder, it exerts a radial component of force on the piston causing increased "drag" against the wall of the cylinder. Ideally, friction and resultant wear between the piston and cylinder walls would be materially reduced if the connecting rod could be arranged to reciprocate in a straight line coincident with the axis of the cylinder.
Another major problem of present day four-cycle internal combustion engines is the inefficient scavenging of exhaust gases from the combustion cylinder prior to the induction of the next fuel charge. In an effort to improve exhaust gas scavenging, the exhaust valve of the conventional four cycle engine is usually timed to open long before the piston reaches bottom dead center at the end of the power stroke. While premature opening of the exhaust valve during the power stroke improves exhaust gas scavenging, it also results in considerable loss of power since the driving force of each piston is applied to the crankshaft for only approximately 130.degree.-150.degree. out of a total 720.degree. of rotation of the crankshaft. Accordingly, the efficiency of a four-cycle internal combustion engine would be materially increased if the driving force of the piston could be applied to the crankshaft over a longer arc of revolution.